/**
 * Copyright 2009-2020 the original author or authors.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.ibatis.submitted.language;

import org.apache.ibatis.builder.BuilderException;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.session.Configuration;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.runtime.RuntimeServices;
import org.apache.velocity.runtime.RuntimeSingleton;
import org.apache.velocity.runtime.parser.node.SimpleNode;

import java.io.StringReader;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;

/**
 * Just a test case. Not a real Velocity implementation.
 */
public class VelocitySqlSource implements SqlSource {

	public static final String PARAMETER_OBJECT_KEY = "_parameter";
	public static final String DATABASE_ID_KEY = "_databaseId";

	static {
		Velocity.setProperty("runtime.log", "target/velocity.log");
		Velocity.init();
	}

	private final Configuration configuration;
	private final Template script;

	public VelocitySqlSource(Configuration configuration, String scriptText) {
		this.configuration = configuration;
		try {
			RuntimeServices runtimeServices = RuntimeSingleton.getRuntimeServices();
			StringReader reader = new StringReader(scriptText);
			Template template = new Template();
			template.setName("Template name");
			SimpleNode node = runtimeServices.parse(reader, template);
			script = new Template();
			script.setRuntimeServices(runtimeServices);
			script.setData(node);
			script.initDocument();
		} catch (Exception ex) {
			throw new BuilderException("Error parsing velocity script", ex);
		}
	}

	public static Map<String, Object> createBindings(Object parameterObject, Configuration configuration) {
		Map<String, Object> bindings = new HashMap<>();
		bindings.put(PARAMETER_OBJECT_KEY, parameterObject);
		bindings.put(DATABASE_ID_KEY, configuration.getDatabaseId());
		bindings.put("it", new IteratorParameter(bindings));
		return bindings;
	}

	@Override
	public BoundSql getBoundSql(Object parameterObject) {
		Map<String, Object> bindings = createBindings(parameterObject, configuration);
		VelocityContext context = new VelocityContext(bindings);
		StringWriter sw = new StringWriter();
		script.merge(context, sw);
		VelocitySqlSourceBuilder sqlSourceParser = new VelocitySqlSourceBuilder(configuration);
		Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
		SqlSource sqlSource = sqlSourceParser.parse(sw.toString(), parameterType);
		BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
		for (Map.Entry<String, Object> entry : bindings.entrySet()) {
			boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
		}
		return boundSql;

	}

	public static class IteratorParameter {

		private static final String PREFIX = "__frch_";
		private final Map<String, Object> bindings;
		private int count = 0;

		public IteratorParameter(Map<String, Object> bindings) {
			this.bindings = bindings;
		}

		public String next(Object prop) {
			StringBuilder sb = new StringBuilder();
			String name = sb.append(PREFIX).append("_ITEM").append("_").append(count++).toString();
			bindings.put(name, prop);
			return name;
		}
	}
}
